COMPARISON OF THE PERFORMANCE OF QUANTUM-WELL AND CONVENTIONAL BULK INFRARED PHOTODETECTORS

Investigations of the performance of quantum well infrared photodetect ors (QWIPs) as compared to other types of semiconductor infrared detec tors are presented. Two types of QWIPs are considered: GaAs/AlGaAs int ersubband quantum well photoconductors and type II staggered InAs/InGa Sb photodiodes. In comparative studies the HgCdTe photoconductors and photodiodes, PbSnTe photodiodes, Schottky barrier photoemissive detect ors and doped silicon detectors are considered. It is assumed that the performance of HgCdTe and PbSnTe photodiodes is due to thermal genera tion governed by the Auger mechanism in the base regions. Investigatio ns of the fundamental physical limitations of HgCdTe photodiodes indic ate better performance of this type of detectors in comparison with Ga As/AlGaAs QWIPs operated in the range 35 to 77 K. In practice however, in temperature range below 50 K the performance of the HgCdTe photodi odes is determined by trap-assisted tunneling. As a result, advantage of GaAs/AlGaAs QWIPs increases in the wider spectral range (below 14 m u m) and temperature below 50 K. This observation plus the maturity of GaAs/AlGaAs technology and its radiation hard characteristics promise that QWIPs technology can produce high quality focal plane arrays (FP As) for space applications. The operating temperature for HgCdTe detec tors is higher than for other types of photon detectors. HgCdTe detect ors with background limited performance operate with thermoelectric co olers in the medium wavelength range, instead the long wavelength dete ctors operate at approximate to 100 K. HgCdTe is characterized by high absorption coefficient and quantum efficiency and relatively low ther mal generation rate compared to extrinsic detectors, silicide Schottky barriers and GaAs/AlGaAs QWIPs. However, the cooling requirements for GaAs/AlGaAs QWIPs with cutoff wavelengths below 10 mu m are less stri ngent in comparison with extrinsic detectors and Schottky barrier devi ces. The theoretically predicted performance of long wavelength InAs/G aInSb photodiodes are comparable with HgCdTe photodiodes. The high per formance of InAs/InGaSb detectors is due to suppression of band-to-ban d Auger recombination rate. (C) 1997 Elsevier Science B.V.